MTC Bio cryogenic vials are designed to hold, store and preserve biological materials for days, weeks, years, or decades. These thick-walled tubes are outfitted with silicone O-rings that allow them to maintain their seal at temperatures as low as -196°C. Sterilized by gamma irradiation, the tubes are packed in reasealable bags of 50 tubes (10 bags per case) and are sterilzied by gamma. The self-standing starfoot base mates perfectly with a FREE included rack so that one hand is all that is need to install and remove caps. RNase, DNase, pyrogen, & endotoxin free